Extended spark discharge systems have the advantage that, after initial breakdown of a spark across the spark plug, subsequent sparks are generated to effect more efficient combustion of the fuel-air mixture. One such system is disclosed in U.S. Application Ser. No. 776,735, filed Mar. 11, 1977, now U.S. Pat. No. 4,181,112, (to which German Disclosure Document DE-OS No. 26 11 596 corresponds). Extended spark discharge systems of that type are particularly suitable for use with electromagnetic storage ignition coils which use a low primary charge current, have high efficiency, and have high recharge current efficiency, so that the overall efficiency of the system is good, and the operating characteristics are excellent. Such electromagnetic storage-ignition systems do have a disadvantage, however, which is particularly apparent at high speeds, and especially in high-speed engines. Due to the relative low charge current, a certain time delay occurs in storing the initial electromagnetic energy needed for breakdown of the spark at the spark plug. Spark advance, that is, the timing of the first breakdown of the spark gap at the spark plug, may not be possible over the entire adjustment range extent, however, particularly at high speeds, since the relatively low charge current causes a delay in storage of sufficient electromagnetic energy in the coil to initiate the first breakdown.
It has previously been proposed to combine the electromagnetic storage principle of spark plugs with capacitor discharge systems--see, for example, U.S. Pat. No. 3,280,809 and German Disclosure Document DE-OS No. 23 38 905; the combination of the two ignition systems--capacitor discharge and electromagnetic storage--of these disclosures is used for an entirely different object, however, particularly in order to ensure reliable ignition even under poor operating and maintenance conditions, for example upon corrosion, dirt, and the like, in contacts and associated elements. The capacitor discharge is used as an override for the electromagnetic discharge system in order to be able to generate sparks with high ignition voltage so that poor electrical condition of the system will not interfere with generation of at least some ignition events.